diff --git a/lib/setup.php b/lib/setup.php
index 41cfa1750abb5b5ab5492a5887f1b607467bd386..f295d69562ed0d3f1eb0bcadde5d4e340d3c4be7 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -99,7 +99,7 @@ class OC_Setup {
 						//use the admin login data for the new database user
 
 						//add prefix to the mysql user name to prevent collissions
-						$dbusername='oc_mysql_'.$username;
+						$dbusername=substr('oc_mysql_'.$username,0,16);
 						//hash the password so we don't need to store the admin config in the config file
 						$dbpassword=md5(time().$password);